I am also worried about my oscars because I fear that I might accidentally overfeed in the process of getting food to the others.
Don't worry since you have a lot of control. Put in 20 floating pellets and 10 sinking pellets all at once and spread out around the tank. All the fish will eat.
After a few minutes, see what is going on. If everyone is still eating and all the food is about gone, you fed too little. If the Oscars have stopped eating and the others haven't, you fed too little. If the Oscars are still eating and the others seem full, you fed the right amount.

If everyone has stopped eating and some food is left, remove it and feed a bit less next time.
Oscars and the other fish are smart enough to figure out there will be lots of food floating and sinking. Once they realize there is a huge feast coming, they'll go for what they see and not worry about what's a foot away.